1. Field of the Invention
The present invention relates to an exhaust silencer or muffler configured to permit relative elongation of an inner cylinder relative to an outer cylinder.
2. Description of the Relevant Art
Exhaust silencers are known in the background art. For example, in an exhaust silencer disclosed in JP-A No. H7-77041, entitled xe2x80x9cmuffler for motorcycle,xe2x80x9d respective front end portions of an outer cylinder and an inner cylinder are integrated with each other, and respective rear end portions of them are configured to be blocked by a tail plate (hereinafter, referred to as xe2x80x9cstepped discxe2x80x9d).
The stepped disc is provided with a small diameter portion (hereinafter, referred to as xe2x80x9cstep portionxe2x80x9d) loosely fitted in the rear end portion of the inner cylinder, and a large diameter portion (hereinafter, referred to as xe2x80x9cenlarged diameter portionxe2x80x9d) tightly fitted in the rear end portion of the outer cylinder. The rear end portions of the outer cylinder and the inner cylinder can be blocked by the stepped disc, by loosely fitting the small diameter portion in the rear end portion of the inner cylinder, and also tightly fitting the large diameter portion in the rear end portion of the outer cylinder.
When the inner cylinder is thermally expanded by heat from exhaust gas, the rear end portion of the inner cylinder slides relative to the step portion, since the step portion in the rear end portion of the inner cylinder is loosely fitted. Thus, the relative elongation of the inner cylinder relative to the outer cylinder is permitted.
When the stepped disc is assembled to the inner cylinder and the outer cylinder, first the step portion of the stepped disc is loosely fitted in the rear end portion of the inner cylinder. Next, the rear end portion of the outer portion is tightly fitted on the enlarged diameter portion of the stepped disc. Thus, when the rear end portion of the outer cylinder is fitted on the enlarged diameter portion of the stepped disc, the stepped disc is liable to be deviate from a regular location.
When the stepped disc is deviated from the regular location, the assembly work to fit the enlarged diameter portion in an opening of the rear end portion of the outer cylinder is difficult. Thus, the assembly process is complicated and time consuming.
In order to eliminate the deviation of the stepped disc from the regular location, the stepped disc may be fixed by using a fixing jig. However, using the fixing jig takes time. The fixing jig must be mounted and dismounted on to, and off of, the stepped disc. Therefore, the fixing jig does not enhance the assembly process from the standpoint of time and complexity.
Thus, there exists a need in the background art to provide an exhaust silencer permitting a relative elongation of an inner cylinder to an outer cylinder, which is easier to assemble.
To achieve the above object, an exhaust silencer according to the present invention includes one end portion of an outer cylinder sandwiching glass wool between the outer cylinder and an inner cylinder, is coupled to one end portion of the inner cylinder having a plurality of expansion chambers inside thereof. The relative elongation of the inner cylinder to the outer cylinder is permitted by blocking the other end portion of the outer cylinder with a stepped disc, and by slidably mounting the other end portion of the inner cylinder on a step portion of the stepped disc.
The structure of the exhaust silencer of the present invention is characterized in that a fuse portion, which is fractured when a prescribed force is presented thereto, is provided at the other end portion of the inner cylinder. The structure of the exhaust silencer is further characterized in that the fuse portion is welded to the step portion of the stepped disc, or to a wall surface constituting the step portion, to temporarily tack the stepped disc to the inner cylinder during a temporary assembly stage. Further, the inner cylinder is separated from the stepped disc by the fracturing of the fuse portion caused by thermal expansion of the inner cylinder, when exhaust gas flows through the inner cylinder.
The fuse portion has a construction capable of temporarily tacking the stepped disc to the inner cylinder by welding the fuse portion to the step portion of the stepped disc, or to the wall surface constituting the step portion. Therefore, when performing assembly work, such as welding of the rear end portion of the outer cylinder to the stepped disc, the deviation of the stepped disc from a regular location is prevented.
Further, the fuse portion is fractured to separate the inner cylinder from the stepped disc, when thermal expansion of the inner cylinder occurs. Thus, the rear end portion of the inner cylinder can slide relative to the step portion of the stepped disc. Therefore, the elongation of the inner cylinder relative to the outer cylinder is permitted.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.